House Minority Whip Steny Hoyer (D-Md.) is pressing his colleagues to back Attorney General Eric Holder when the House votes on whether to hold him in contempt of Congress on Thursday, but Democrats are bracing for defections.

The reason? The National Rifle Association.

The gun rights group announced June 20 that it is scoring the contempt vote, ratcheting pressure on Democrats in marginal districts who count on its support to bolster their appeal to voters for whom the Second Amendment is paramount.

The problem was illustrated vividly Tuesday, when Rep. Jim Matheson (D-Utah), a Blue Dog and perennial target of Republicans who faces an uphill battle this year, said he would vote to hold Holder in contempt because of his &ldquo;evasiveness&rdquo; on House Republicans&rsquo; investigation of the botched &ldquo;Fast and Furious&rdquo; gun-smuggling operation.

&ldquo;Utahns expect and deserve transparency and accountability from government officials. ... Sadly, it seems that it will take holding the Attorney General in contempt to communicate that evasiveness is unacceptable. It is a vote I will support,&rdquo; Matheson said in a release.

Hoyer acknowledged he would bleed votes because of the NRA&rsquo;s involvement. But asked to estimate how many, the Maryland Democrat said, &ldquo;I can&rsquo;t.&rdquo;

The NRA&rsquo;s involvement on a vote that will not directly affect gun laws is an aggressive move for an organization that has recently faced complaints from the right that it isn&rsquo;t partisan enough.

It prompted some Democrats to privately convey their anger at the decision to NRA lobbyists.

Hoyer criticized a letter from Chris Cox, executive director of the NRA&rsquo;s Institute for Legislative Action, announcing the organization&rsquo;s decision to score the vote, drawing a blistering response from the gun group.

&ldquo;Mr. Cox says we are no fan of Mr. Holder&rsquo;s. Now, why that is necessary to be stated in the letter other than to point out that they are opponents of Mr. Holder and have been since he was sworn in ...&rdquo; Hoyer said, trailing off.

NRA spokesman Andrew Arulanandam said, &ldquo;For anyone to claim this is politically motivated is not only inappropriate, but it is, frankly, thoughtless.&rdquo;

A Democratic aide said the decision could hurt the NRA&rsquo;s credibility. A second Democratic aide said, &ldquo;Voters are already so frustrated at what they see as Washington focusing on the wrong issues, and this reinforces that.&rdquo;

But Republicans feel political momentum is on their side.

Two GOP aides who had previously expressed concern that House Oversight and Government Reform Chairman Darrell Issa&rsquo;s (R-Calif.) contempt push was distracting from their party&rsquo;s economic message now expressed a different view, saying Republicans&rsquo; focus on murdered Border Patrol agent Brian Terry was paying off politically. Two guns traced back to Fast and Furious were found at the scene of Terry&rsquo;s murder.

&ldquo;Issa is a pretty shrewd operator. And ultimately, whether you think the contempt vote is bad or not, every day you talk about it, you have to talk about Brian Terry and that he was shot because the administration walked guns to Mexican drug cartels. Something tells me it&rsquo;s working,&rdquo; the first aide said.

The issue works on multiple levels, the second aide said. &ldquo;The contempt of Holder is a dog whistle to the right-wing tea party community, saying that we are representing them. They&rsquo;re upset we haven&rsquo;t done more on spending, etc. But this is a way to say we&rsquo;re going after this administration, holding them accountable.&rdquo;

It&rsquo;s a quick turn of events, considering gun issues had been dormant for years.

Now, in part because of the vote, gun issues have vaulted to the forefront for many Republicans, even as President Barack Obama has been largely absent from pushing gun control.

&ldquo;Obama&rsquo;s leadership on gun issues has been extremely disappointing,&rdquo; said Dan Gross, president of the Brady Campaign to Prevent Gun Violence. &ldquo;His voice has been completely missing.&rdquo;

That hasn&rsquo;t settled suspicions on the right, where activists discuss far-fetched theories about how Fast and Furious was launched as a scheme to create a gun violence problem that only new laws could solve.

In Fast and Furious, agents for the Bureau of Alcohol, Tobacco, Firearms and Explosives allowed assault guns bought by &ldquo;straw purchasers&rdquo; to &ldquo;walk,&rdquo; which meant ending surveillance on weapons suspected to be en route to Mexican drug cartels.

The tactic, which was intended to allow agents to track criminal networks by finding the guns at crime scenes, was condemned after two guns that were part of the operation were found at Terry&rsquo;s murder scene.

Straw purchasers are individuals who buy guns on behalf of criminals, obscuring who is buying the weapons.

&ldquo;It&rsquo;s going to bring a lot of attention to straw purchasing of assault weapons,&rdquo; former U.S. Attorney Dennis Burke wrote about Fast and Furious in a November 2010 email.

&ldquo;Some of the weapons bought by these clowns in Arizona have been directly traced to murders of elected officials in Mexico by the Cartels, so Katy-bar-the-door when we unveil this baby,&rdquo; Burke said.

Burke, once a rising star in the Democratic Party, told the Arizona Business Gazette in 1997 that pushing new gun regulations in the Clinton White House was the most fulfilling professional assignment he&rsquo;d had. Burke resigned after Fast and Furious became a controversy.